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What is the difference between T12 and T8 bulbs?

This is a question we often get asked and the answer is very simple. On the most basic level, the T12 and the T8 bulbs have a different diameter tube thickness. The T12 is 1.5 inches in diameter and the T8 is 1 inch in diameter. Many years ago, the research found out that if they could make the light tube thinner, then there would also be greater energy efficiency associated with it. That led to the development of different kinds of ballasts to accommodate this newer type of 1-inch diameter tube. T12 and T8 lamps also differ on the ballast that they are operated with most of the time. T12 primarily run off a magnetic ballasts and T8 bulbs operate on electronic ballasts. That's not always the case as sometimes people changed their T12 ballast to be electronic years ago. But most people have them operating on a magnetic ballast. Even though the fluorescent light socket is exactly the same for both of them, they cannot operate on the same ballast. If you try to put a T12 lamp in an electronic ballast, it will generally flicker a lot and have some problems even though it may light up. It's not made electrically for that type of ballast, the T8 light bulb is. It's engineered differently to operate best on electronic ballasts of various types whether it be an instant start or a program start. Most commercial buildings and people that use them in their homes have the instant start ballast that operates the T8 light bulb. So the bottom line is that these are not interchangeable and if you're going to upgrade from a T12 to a T8 bulb, then you also have to change out the ballast. Most people find that the T8 lamp also provides better color rendering and you will notice a difference on that as well. So it's more than just energy efficiency, it's also the effect that it has. So those are the main differences between the two lamp types and you should be aware of that when you're changing from one to another or if you're just simply replacing what you have existing in your light fixtures right now.

Although T8 tubes are often employed to get better energy savings than the older style fluorescent tubes, the effect is basically the same as any other linear fluorescent. It’s a length of phosphor-coated tube that went powered on excites the phosphors which create visible light. So there’s nothing greatly different about the actual concept between T12 and T8 except that one is more efficient than the other. It was discovered many years ago that if you could bring the tube to a narrower diameter, efficiencies of the light bulb itself would be increased. This spawned a whole new variety of fluorescent lighting that continues to be used to this day. Now the changes coming with many LED tubes replacing even the T8’s. LED tube lights work in the same sockets as the T8 and possibly the T12 depending on what you have, making them an obvious retrofit opportunity with a fast payback. The other thing that’s changed is that color temperatures became more precise over time. Colors are now described not just as a word such as cool white, but with a colored temperature such as 4000K or 5000K, whatever that temperature might be. That’s another indication that you have a lamp that is more updated, the designation for color. Another improvement that came along with T8 bulbs was an improved color rendition as well. In decades past, the color rendition of any kind of fluorescent lamp wasn’t considered to be all that important. It was simply making the cheapest lamps possible for a marketplace that was exploding with the possibilities of fluorescent lighting. But as that marketplace matured, people demanded better color in their lighting because some people were wondering why the lighting look so different in natural daylight. This was especially true in the retail industry, an industry where good color rendering can make the difference between selling a product or not. It was largely driven by that and when other people start to see that it would work great for an office situation, improving productivity then it was also adopted there. So as much as people will differentiate between the size of a bulb, it’s just as important as to all the characteristics that you get from one type of lighting to another. T12 bulbs are simply an older technology that arose back in the 1940’s which was a big step forward in lighting. It took a very long time but finally back in the mid-80s, T8 lamp technology was introduced and became the new standard for energy efficiency and people began moving to that type of lighting. The adoption of T8 lighting took some time because people not only had to just change a light bulb, but they had to change a ballast as well. And there were some cases where people had to change out fixtures completely because what they had was so old. It was that economic consideration that sometimes retarded the move to more efficient T8 lamps. Now with the advent of LED T8 bulbs, people can now move into something that’s even more energy-efficient and won’t have to have a ballast anymore if they don’t want it. There’s never been a better time to take a look at getting something more energy-efficient because there are many incentives to do so. The good news is that the sockets that are being used today in T8 light fixtures, can be used for the LED T8’s that are coming out on the market all the time. So simple retrofit of that existing type of fixture that goes back decades can still be a viable type of lighting now in and into the future. Take a look at all the different types of LED light fixtures on our website that utilize this type of T8 configuration and you’ll probably find something that will work great for you. Also, let us know if we can help you determine what might be the best way to go for more efficient lighting.

I hope that answers your question, let us know if there's anything else we can help you with.

John Bolduan

Phone 866-637-1530
Text 651-324-1409
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